1. Field of the Invention
The present invention relates to a dynamic damper to be mounted on a rotary shaft, such as the drive shaft or propeller shaft of an automobile, to damp detrimental vibrations generated as the rotary shaft rotates, such as naturally undesirable bending and torsional vibrations.
2. Description of the Prior Art
As shown in FIG. 7, a conventional, generally used dynamic damper comprises an elastic member 100 fixedly mounted on a rotary shaft S, and a tubular mass member 200 combined integrally with the elastic member 100 and having an inside diameter greater than the outside diameter of the rotary shaft S. The elastic member 100 has two tubular holding portions 101 and two elastic, radially extending end portions 102 integrally combined respectively with the tubular holding portions 101. The spring constant of the elastic member 100 is adjusted properly by selectively determining its quality of shape or the mass and/or the mass member 200 is determined selectively to adjust the characteristic frequency of the elastic member 100 to the frequency of the principal detrimental vibration. Thus, the detrimental vibrations of the rotary shaft S are damped by converting the vibrational energy of the rotary shaft S into that of the dynamic damper by the agency of resonance.
Since the frequency of the principal detrimental vibration is dependent on the construction and rotating speed of the rotary shaft, and the conventional dynamic damper is provided integrally with the elastic member and the mass member, dynamic dampers of different specifications must be manufactured for application to various kinds of rotary shafts. That is, having only a single characteristic frequency corresponding to the frequency of a single detrimental vibration, the conventional dynamic damper is function effectively merely for damping a single detrimental vibration. Accordingly, various dynamic dampers respectively for damping various detrimental vibrations must be manufactured for use in combination with different rotary shafts. However, the preparation of materials of different compositions for forming elastic members respectively having different characteristics and the formation of the elastic members respectively in different shapes require troublesome work and much time and labor, and the mass member of the conventional dynamic damper is liable to obstruct the removal of the dynamic damper from the mold after vulcanization, which is disadvantageous in respect of mass production of dynamic dampers. Thus, the conventional dynamic damper has difficulties in its application to damping various kinds of detrimental vibrations.